1. Field of the Invention
This invention is applicable to the field of catalytic hydrocarbon conversion. The invention relates to a novel catalyst for use in a hydrocracking process. More specifically, it relates to an improved hydrocracking catalyst which demonstrates unexpected and exceptional activity, selectivity and resistance to deactivation when employed in a hydrocracking process producing middle distillates from heavy gas oils and the like under hydrocracking conditions.
Many refineries today produce middle distillate products such as jet fuel and diesel fuel by hydrocracking a heavy gas oil charge stock. The charge stock usually has a boiling point in the range between about 650.degree.-1050.degree. F. The hydrocracking products are obtained by contacting the heavy oil at an elevated temperature and pressure in the presence of hydrogen with a suitable hydrocracking catalyst. The middle distillate fraction which is uncovered has a boiling range between about 300.degree.-700.degree. F. A main concern of refineries today is to increase middle distillate production via the hydrocracking process. By improving the catalytic properties of the catalyst employed in the hydrocracking process, middle distillate production can be increased.
Activity, selectivity and stability are the three main catalytic properties by which a hydrocracking catalyst is evaluated. Activity usually is determined by comparing the temperature at which various catalysts must be utilized under otherwise constant hydrocracking conditions with the same feedstocks and same conversion rate of products boiling below a specified temperature. The lower the activity temperature for a given catalyst, the more active the catalyst is for the specified process. Selectivity of hydrocracking catalysts is a measure of the yield of a desired product. Stability is a measure of how well a catalyst maintains its activity and selectivity over an extended period of time when treating a given hydrocarbon feedstock. Stability is generally measured in terms of the rate of change in temperature required per day to maintain a given conversion rate.
The goal of hydrocracking catalysis is to provide a catalyst with the highest possible activity, selectivity and stability. Catalysts employed in hydrocracking processes usually comprise a Group VIII metal component in combination with a Group VIB metal component, both of which are in intimate admixture with a support material. The activity, selectivity and stability of the catalysts vary widely when different supports are used. Support materials known to the hydrocracking art comprise porous refractory inorganic oxide materials such as amorphous silica alumina, alumina and the like, as well as crystalline aluminosilicate zeolites, such as zeolite-Y. Support materials consisting essentially of refractory oxides generally have relative poor activity, but high selectivity, while support materials comprising zeolites generally provide high activity, but low selectivity.
2. Object of the Invention
An object of the present invention, therefore, is to provide a hydrocracking catalyst having superior catalytic properties for hydrocracking hydrocarbons. More specifically, it is an object of this invention to provide a catalyst having superior activity, selectivity and stability for hydrocracking in comparison to prior art catalysts. Further, it is an object of this invention to provide a hydrocracking catalyst having superior catalytic properties for converting heavy gas oils to middle distillate products. Additionally, it is an object of this invention to provide a support or carrier material which may be useful in a hydrocracking process. It is also an object to provide a superior hydrocracking process for the conversion of heavy gas oils to middle distillate products. These and other objects and advantages of the present invention will become more apparent in view of the following description of the invention.
3. Description of the Prior Art
A number of patents disclose cracking catalysts comprising a mixture of zeolites dispersed in an inorganic oxide matrix.
U.S. Pat. No. 4,419,271 discloses a hydrocracking catalyst for use in the production of middle distillate oils comprising one or more hydrogenation components supported on a base containing a crystalline aluminosilicate zeolite and a dispersion of silica-alumina in an alumina matrix. Patentee teaches that a mixture of one or more crystalline aluminosilicates having cracking activity may be dispersed in the double matrix. Patentee, however, does not disclose any specific mixture of zeolites.
U.S. Pat. No. 4,287,048 discloses a hydrocracking catalyst comprising an ultra-stable Y-type zeolite and a small pore crystalline zeolite such as mordenite in an inorganic oxide matrix.
U.S. Pat. No. 4,137,152 discloses a cracking process utilizing a mixture of faujasite and mordenite.
U.S. Pat. No. 3,894,934 discloses catalytic cracking of hydrocarbons utilizing a large pore zeolite and a small pore zeolite such as zeolite ZSM-5 dispersed in a common matrix.
U.S. Pat. No. 3,702,886 discloses use of ZSM-5 zeolite alone or in combination with other materials such as zeolites or inert materials for catalytic cracking of hydrocarbons.
U.S. Pat. No. 3,804,747 discloses a hydrocarbon conversion process utilizing a mixture of zeolites X and Y.
U.S. Pat. No. 3,758,403 discloses a catalytic cracking composite comprising a large pore zeolite, such as zeolite Y, and a small bore zeolite, such as ZSM-5, in a siliceous matrix. The matrix may be active or inactive, such as silica-alumina or alumina. The use of the ZSM-5 type zeolite results in obtaining a fuel of increased octane number.
U.S. Pat. No. 3,769,202 discloses a combination catalyst comprising a mixture of two different zeolites, one having a pore size greater than 8 Angstroms and the other having a pore size of less than 7 Angstroms. The zeolites are mixed with an inorganic oxide matrix such as silica-alumina. The catalyst is suitable for cracking and hydrocracking of hydrocarbons.
U.S. Pat. No. 3,925,195 discloses a cracking process utilizing a catalyst comprising a mixture of rare earth hydrogen Y-type zeolite, and hydrogen or transition metal-exchanged mordenite, calcium-exchanged type A zeolite, or hydrogen-exchanged erionite and an amorphous matrix.
U.S. Pat. No. 3,764,520 discloses a catalyst comprising a mixture of two different zeolites, one having a pore size within the range of 6 to 15 Angstroms and the other having a pore size of less than 6 Angstroms in combination with an inorganic oxide support. The catalyst is useful for hydrocarbon conversion processes to give increased selectivity.
None of the above-mentioned patents, however, disclose a catalytic composition comprising a specific mixture of Y-type zeolites.